Cron script does not finish

I have a cron that runs an SVN dump script which does not finish. About 1/4 of the data gets dumped and the process ends. The script looks like:
#!/bin/bash
svnadmin dump /usr/local/svn > /usr/local/backupscripts/dump/Dailydump
The script works when launched on the command line but the cron dies.
Are there any restrictions or modifications that I can make that will allow this to finish?

The problem might be as previously suggested, the ENV for cron is not the same as it is for your command line.

Make sure the cron job is executing the programs you think it is. I used one that was giving me trouble until I verified the programs that were being used on the command line and then explicitly invoked the same ones with a full path to each executable in the cron script.

Thanks to all of you for your suggestions.
The problem was that the process ran for about three hours and for some reason it was killed in about 20 minutes. The use of:
nohup nice svnadmin dump /usr/local/svn > /usr/local/svn/dump/svnDaily -q &
fixed the problem and we get a full dump every night